Pressure sensitive fluoran derivative containing copying paper



United States Patent 3,501,331 PRESSURE SENSITIVE FLUORAN DERIVATIVE CONTAINING COPYING PAPER Shiro Kimura, Teruo Kobayashi, and Sadao Ishige, Kanagawa, and Shizuo Katayama, Fujimiya-shi, Japan, assignors to Fuji Shashin Film Kabushiki Kaisha, Kanagawa, Japan N0 Drawing. Filed Jan. 29, 1968, Ser. No. 701,118 Claims priority, application Japan, Jan. 27, 1967, 42/ 5,327 Int. Cl. B41m /02 US. Cl. 117--36.2 2 Claims ABSTRACT OF THE DISCLOSURE A pressure sensitive copying paper having thereon a layer containing as a color former at least one of the fluoran derivatives represented by the general formula,

wherein R and R each represents an alkyl group having less than 5 carbon atoms and R and R each represents a member selected from the group consisting of a hydrogen atom, a benzyl group and an alkyl group having less than 5 carbon atoms.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a pressure sensitive copying paper, and more particularly, it is concerned with a pressure sensitive copying paper containing a fluoran derivative as a color former.

Description of the prior art The ordinary pressure sensitive copying paper consists of an upper sheet coated with an electron donating, colorless organic compound which will be referred to as color former in such a form that it is dissolved in an oil and enveloped in fine capsules, and an under sheet coated with an electron accepting, solid acid by the use of a suitable binder. The sheets are superposed in such a manner that the coating surfaces are faced. When the copying paper is partially pressed by hand writing or type writing, the capsules in the pressed part are ruptured and the colorless color former is adsorbed on the solid acid, followed by color forming. Other pressure-sensitive copying paper has been proposed in which an intermediate sheet carrying a color former on the back side and a solid acid on the right side is held between an upper sheet and an under sheet.

As an electron accepting solid acid are known clays such as acid clay, active clay, bentonite, attapulgite, zeolite, kaolin, organic acids, and phenols.

As an electron donating color former are known Rhodamine Lactone, Rhodamine Anilinolactam, Crystal Violet Lactone, Malachite Green Lactone and Benzoyl Leucomethylene Blue.

Among these color formers, Rhodamine Lactone has the defect that a red-color fog is rapidly formed with the passage of time due to its instability, Rhodamine Anilinolactam has the defect that it requires several minutes until a partially pressed part be completely colored in red although it is stable, Crystal Violet Lactone has the defect that a pressed and color-formed part be rapidly faded with moisture or sunlight although it is rapidly colorformed in violet-blue, Malachite Green Lactone has a defect that, although it is color-formed in blue, it requires about 2 minutes until color-formed completely, the color density is relatively low and the light resistance is weak, and Benzoyl Leucomethylene Blue is color formed in blue-green and excellent in the water and light resistance, but its color forming speed is very slow (longer than about 1 hour).

Where it is desired to obtain a pressure sensitive copying paper color forming in black by the use of a yellow color former together with the aforementioned color former, there occurs often an uneven color forming due to differences in the color forming speed, water resistance and light resistance thereof, and the desired pressure sensitive copying paper, that is, color forming satisfactorily in black is scarcely given.

It is the principal object of the invention to provide a pressure sensitive copying paper capable of color forming in black or green-black with a single color former and to provide another pressure sensitive copying paper capable of color forming in a suitable color such as blueblack by the joint use of a known color former.

SUMMARY OF THE INVENTION The feature of the invention consists in a pressure sensitive copying paper in which a fluoran derivative represented by the following general formula is incorporated as a color former,

N-I; 6 3 R2 2 N/ wherein R and R each is an alkyl group having less than 5 carbon atoms and R and R each is a hydrogen atom, a benzyl group or an alkyl group having less than 5 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION The following table may be referred to for examples of the color formers used in the invention and of its synthesis.

General formula Color former R R2 R R4 Chemical name CH3 OH; H 3-dimethylamino-7methylamino-fluoran. CZH H H 3-diethylamino-7-amino-fluoran. 021-1 OH; H 3-diethylamino-7-methylamino-fluoran. CzHs C2H5 H 3-diethylamino-7-ethylamino-fluoran. C2H C2115 C2115 3,7-bis-diethylaminofluoran. C zHs n-C4H9 H 3-diethylamino-7-(n-butylamino)-fluoran. C2115 sec-C4Ha H 3-diethylan1ino-7-(sec-butylamino)-fluoran' No. 8 CzHs CzHs CH2@ H 3-diethylamin0-7-benzylaminofluoran.

The general synthesis method is as follows:

COOH

Intermediate A In this equation, R R R and R have the same meaning as in the general formula and R is a hydrogen atom or a lower alkyl group.

One mole of ortho-(4-dialkylamino-2-hydroxybenzoyl)-benzoic acid and 1-1.2 moles of para-aminophenol derivative are dissolved in 1 20 moles of concentrated sulfuric acid and reacted at 8()1()0 C. for 36 hours. After the reaction, the reaction solution is cooled to room temperature, poured in a large amount of ice water and neutralized with an aqueous solution of alkali such as caustic soda to be weakly alkaline. The deposited crystals are filtered under suction or extracted with chloroform and concentrated to dryness, and the resulting crude product is recrystallized with toluene, benzene or acetone.

Another synthesis method, which is limited to the case where R =H in the general formula, is as follows:

In this equation, R R and R have the same meaning as in the general formula, R is hydrogen atom or a lower alkyl group and R is a lower alkyl group or aryl group.

One mole of ortho-(4-dialkylamino-Z-hydroxybenzoyl)- benzoic acid and 11.2 moles of a para-acylaminophenol derivative are reacted in concentrated sulfuric acid at 2050 C. for 2()50 hours, and the reaction solution is poured in a large amount of ice water to give a precipitate. This precipitate is heated in dilute hydrochloric acid or sulfuric acid at 100 C. for 3-6 hours to release the acyl group (COR') and neutralized with an aqueous solution of alkali to obtain an object product.

Synthesis examples of the intermediate product A will be illustrated hereinafter.

Synthesis of ortho-(4-diethylamino-Z-hydroxybenzoyl)- benzoic acid -011 \O in toluene H502 I boiling C tl /N 0 II H 0 660 g. (4 moles) of metha-diethylaminophenol, 592 g. (4 moles) of phthalic anhydride and 3000 ml. of toluene are heated and refluxed for 45 hours. The reaction product is gradually crystallized from the reaction solution. After cooling to room temperature, the product is filtered under suction and washed with methanol to obtain 92 0 g. of crystals (yield: 74%). The crystal melting at above C. turns red and decomposes by heating and melts completely in dark red-violet at 207 .C. (D.P. 85931, Fliedlander vol. 4, p. 260.)

Synthesis of ortho-(4-dimethylarnino-Z-hydroxybenzoyl)-benzoid acid The object product is obtained in a yield of 45-50% by the similar procedure to the foregoing reaction except using m-dimethylaminophenol in place of m-diethylaminophenol.

Synthesis examples of the color former are given below.

Synthesis Example 1 (color former No. 1)

Using ortho (4 dimethylamino-Z-hydroxybenzoyl)- benzoic acid (R =CH R2=CH in the intermediate product A) and para-methylaminophenol (R =CH R ='I-I, R=H in the intermediate product B), anisole derivative (R=CH or phenetole derivative (R=C H the mixture is processed similarly to the general synthesis method and subjected to the dehydrating reaction (in the case of R=H) or alcohol removing reaction (in the case of R=CH and C H in concentrated sulfuric acid to give crude crystals. Recrystallization thereof from toluene gives white crystals melting at 245-6 C.

Synthesis Example 2 (color former No. 2-No. 8)

This example is similar to the synthesis Example 1 except using the intermediate product A and intermediate product B corresponding to each color former. In

each case, a color former of white crystals is obtained, which melting point is shown in the following table.

ening, and allowed to stand for several hours to accomplish the capsule making operation. The so obtained Synthesis Example 3 (color former No. l-No. 8 except No. 5)

One mole of ortho-(4-diethylamino-2-hydroxybenzoyl)- benzoic acid and 1 mole of para-acetamino (or benzoylamino) phenol are used and processed as in the other synthesis method to give Color Former No. 2. This crystal is identical with that of Synthesis Example 2 (color former No. 2) obtained by the general synthesis method in respect of M.P., infrared analysis, C.H.N. analysis and HMR. Color formers No. l-No. 8 except No. 5 are similarly synthesized by the use of the corresponding raw material.

In the porduction of the pressure sensitive copying paper of the invention using the foregoing color former, the method well known in the art from US. Patent 2,548,366; 2,800,457 and 2,800,458, that is, for making microcapsules by utilizing the phenomenon of composite coacervation is employed. The present invention provides a pressure sensitive copying paper containing a special compound having the foregoing general formula as a color former, which characteristics are independent upon the process for producing a pressure sensitive copying paper.

Accordingly, the invention is not limited to the production process. The amount of color former to be added is ordinarily 1-5% by weight of an oily solvent.

Thep ressure sensitive copying paper is colorless before color forming and stable without formation of the natural color forming fog even though allowed to stand in the air. In the case of color forming under pressure, the color forming occurs instantaneously in a color tone of black to green-black. This is a color tone capable of being copied on the diazo sensitive paper, since almost the whole visible region of about 410 mg to 650 m is absorbed, the absorbing extending to the spectrum region of about 350 mg to 420 m corresponding to the sensitive region of diazo sensitive paper. Moreover, the color density of black is high and the water and light resistances are excellent. Furthermore, a pressure sensitive copying paper having simultaneously the color former represented by the foregoing general formula and the known color former of yellow, red, violet, blue or blue-green can color form in a suitable blackish color so as to be adapted to use, without meeting the desensitizing due to their interaction.

The following examples are given in order to illustrate the invention without limiting the same.

EXAMPLE 1 Three g. of each of Color Former No. l-No. 8 was taken and processed by the following procedure. It was dissolved in 100 g. of diphenyl trichloride and added to a solution of 20 g. of gum arabic and 160 g. of water to cause emulsification. Then, a solution of 20 g. of acid treated gelatin and 160 g. of water was added thereto, acetic acid was added With stirring to lower the pH to 5 and 500 g. of water was added to cause coacervation. At that time, a thickened liquid film of gelatin and gum arabic was formed round the oil drops dissolving the color former. Then, the pH was lowered to 4.4 and 4 g. of 37% Formalin was added for hardening. During the same time, the temperature was kept at 50 C. The mixture was then cooled to 10 C. to gelatinize the thickened liquid film, the pH being raised so as to promote the effect of hardcapsule liquid was applied to a sheet of paper by a coating method such as roll coating or air knife coating and dried. The resulting paper (upper sheet) was superposed on a clay paper (lower sheet) coated with the foregoing clay material and subjected to writing under pressure. Consequently, there appeared instantaneously a color tone on the clay paper, black in Color Former No. 1, blackbrown in No. 2, black in No. 3 and No. 4, green-black in No. 5, and black in No. 6,-No. 7 and No. 8. In the case of using bentonite, these color formers turned greenish as compared with other clays. The coloring matter thus color forming was not faded even though wetted with glycerine or water, or exposed to the sunlight for a long time. When each of the upper sheets thus coated was heated at C. for 20 hours or exposed to the sunlight for a long time, there occurred no deterioration in the color forming character. The light, water and heat resistances before and after color forming exhibited a practically suflicient stability to the passage of time.

EXAMPLE 2 This example is similar to Example 1 except that 1 g. of Color Former No. 3, 1 g. of Color Former No. 5, 0.5 g. of Malachite Green Lactone (or 0.3 g. of N-Phenyl Leuco Auramine, blue color former) and 0.5 g. of Benzoyl Leucomethylene Blue are jointly used. A pressure sensitive copying paper was obtained color forming in blue-black on the clay paper.

What is claimed is:

1. A pressure sensitive transferring sheet adapted to be used in conjunction with a receiving sheet having an electron accepting layer to form a pressure-sensitive copying assembly, said transferring sheet comprising a support and coated on said support, a layer containing pressure-rupturable microcapsules, said microcapsules containing oil and dissolved therein a coloring agent comprising at least one of the fiuoran derivatives represented by the general formula,

wherein R and R each represents an alkyl group having less than 5 carbon atoms and R and R, each represents a member selected from the group consisting of a hydrogen atom, a benzyl group and an alkyl group having less than 5 carbon atoms.

2. The pressure sensitive copying paper as claimed in claim 1 wherein said fiuoran derivative is selected from the group consisting of 3-dimethylamino-7-methylaminofiuoran, 3-diethylamino-7-amino-fiuoran, 3-diethylamino- 7-methylamino-fluoran, 3-diethylamino 7 ethylaminofiuoran, 3,7-bis-diethylamino-fiuoran, 3-diethylamino-7- (n-butylamino)-fluoran, 3-diethylamino 7 (sec-butyl- 7 8 A amino)-fiuoran, and 3-diethylamino 7 benzylamiiio- 3,336,337 8/1967 Gosnell 117-36.2 fluoran. 3,427,180 2/1969 Phillips 117-36.2

References Cited MURRAY KATZ, Primary Examiner UNITED STATES PATENTS 3,020,171 2/1962 Balcan et a1. 11736.2 5 US' Cl X'R' 3,244,550 4/1966 Farnham et a1 11736.2 60-2433 

